How Does Bridging Bony Growth in the Spine Affect Range of Motion & Fracture Risk?

Diffuse idiopathic skeletal hyperostosis (DISH) is a spinal condition that causes excessive bony growth that spans multiple vertebrae, effectively "fusing" the spine. People with DISH often have no symptoms and may not even know they have it until they have another reason to obtain radiological imaging.

The effect of this condition on the spine's ability to bend and its susceptibility to fracture had not been previously quantified. That's why Exponent's biomechanical experts Elizabeth Rapp van Roden, Corinne Riggin, Derek Holyoak, Dhara Amin, Patrick Hall, Juan Paredes, Ryan Siskey, and Michael Carhart conducted a study on the flexibility of DISH-affected spines, which has recently been published in the scientific journal Annals of Biomedical Engineering. 

In their study, the researchers examined human cadaveric DISH-affected and normal spinal segments to evaluate the differences in their mechanical behavior. The spinal segments underwent range of motion testing and extension to failure using a custom test fixture built by Exponent. The research team found that the DISH-affected spinal segments were significantly less flexible and significantly more likely to fracture. In fact, spinal segments with DISH were sixteen times more likely than normal segments to fracture for a given amount of extension bending. 

The study provides the first quantitative evidence of increased fracture risk in DISH spines, supporting clinical observations of the vulnerability of these patients to injury even under low-energy events, like a moderate car accident. 

From the publication: "Future work classifying the severity of DISH in the context of mechanical response may assist in radiological identification of otherwise asymptomatic patients with increased potential for injury."